The biological effects of short-medium chain fatty acids have been studied recently. It has been revealed that a short chain fatty acid exhibits the physiological actions shown below and a medium chain fatty acid exhibits the 6th action among the list.
1. Promotes growth of intestinal epithelial cells.
2. Activates intestinal movement and ion transportation, i.e. absorption of water and ions.
3. Increases blood flow in the large intestinal mucosa.
4. Increase mucus secretion in the large intestine.
5. Adjusts endocrine secretion, including promotes insulin secretion and prevents catabolic hormone secretion.
6. Promotes pancreatic exocrine function or digestive fluid secretion.
7. Affects on the bacterial flora in the large intestine, including stimulates growth of lactic acid fermentation bacteria and suppress growth of escherichia colis. 
8. Promotes cell differentiation and apoptosis.
When the short chain fatty acids are orally administered, almost all of the administered acids are absorbed from stomach and small intestine and the acids hardly get to the large intestine. Accordingly, in the conventional studies, oral administration of various resistant starches or water soluble dietary fibers; and enema administration of short chain fatty acids have been employed for delivering the short chain fatty acids to the large intestine. The orally administered resistant starches or water soluble dietary fibers pass through the gastrointestinal tract without being digested, reach to the large intestine, and in the large intestine, part of them are easily digested into short chain fatty acids by the fermentation action of bacterial flora in the large intestine.
In these days, effects of short chain fatty acids, including anti-inflammatory effect, anti-proliferative effect against tumor cells, differentiation enhancing effect and apoptosis inducing effect have been revealed and the short chain fatty acids have been tried or proposed to be applied for treating or preventing a various diseases. For example, non-patent references 1-3 disclose effects of short chain fatty acids on inflammatory bowel disease, diarrhea, colon cancer and the like.
It has been reported that due to its anti-inflammatory effect, a short chain fatty acid is useful for treating inflammatory bowel disease including ulcerative colitis, Crohn's disease, pouchitis, ischemic colitis, diversion colitis, and radiation proctitis. In addition, it has been reported that the short chain fatty acid is effective for treating large bowel cancer because of its apoptosis inducing effect on tumor cells (see non-patent references 4-7).
Among the inflammatory bowel diseases, ulcerative colitis and Crohn's disease, which are associated with formation of erosions or ulcers of unknown etiology, are hard to cure and include repeated active and remission stages. Drug therapy has been tried to inhibit the inflammatory during the active stage and lead the patient to the remission stage, and to prolong the remission stage period. In many studies, administering the short chain fatty acids to the large intestine by means of enema or oral administration of water soluble dietary fibers has been reported effective for preventing or treating said disease (non patent references 8-11).
In addition, effect of the short chain fatty induced by oral administration of water soluble dietary fiber or by the short chain fatty acids enema or intestinal infusion for treating the other inflammatory disease with similar conditions such as diversion colitis, pouchitis, ischemic colitis, radiation proctitis and colitis caused by bacterial infection such as Shigella have been reported (non patent references 12-15).
It has been reported that upon treating those diseases with a short chain fatty acid, diarrhea associated with said disease is also relieved. This effect might be due to the water absorption improving effect of the short chain fatty acids. With respect to the effect on diarrhea, it was also reported that oral administration of resistant starch or water soluble dietary fiber, and intestinal infusion of a short chain fatty acid were effective on acute diarrhea including choleraic and non-cholearaic diarrhea, and persistent diarrhea including non-pathogenic diarrhea and infectious diarrhea due to rotavirus, cholera bacterium, salmonella or toxic pathogenic Escherichia coli infection (non patent references 16-19).
On the other hand, it was also reported that resistant starch and water soluble dietary fiber were effective for improving bowel movement and treating constipation due to the effect of a short chain fatty acid to promote movement of the large intestine (non patent references 20-22).
Oral administration of water soluble dietary fiber to patients suffered from diarrhea-predominant, constipation-predominant or mixed type irritable bowel syndrome has been reported to be effective in relief of the condition. It was also reported that non-water soluble dietary fiber, which is hardly digested by the action of intestinal fermentation and provides only small amount of short chain fatty acids, was not effective on IBS (non-patent references 23 and 24).
Administration of resistant starch has been reported to decrease neutral fats, phospholipids, cholesterols and the like in the blood (non patent references 25 and 26). Non-patent reference 27 proposes the mechanism as follows: the resistant starch is fermented and absorbed in the large intestine, the stimulation is transmitted to the short intestine and the release of fatty acid from the short intestine to the circulation system is suppressed.
Some other effects of a short chain fatty acid such as inhibiting tumor cell growth, promoting cell differentiation and inducing apoptosis have also been reported and based on those effects, many people have tried to use some short chain fatty acids for preventing or treating large bowel cancer such as colon cancer and rectal cancer. To date, many studies on the administration of various dietary fibers for reducing the risk of or preventing the onset of large bowel cancer have been reported. Relationship between the amount of generated short chain fatty acids and the cancer inhibitory effect has been reported and the role of the short chain fatty acids on inhibiting cancer is suggested (non-patent references 28 and 29). Effect of short chain fatty acids enema for preventing onset of cancer has also been reported (non-patent reference 30).
The short chain fatty acid affects differently on different stages of developing tumor from normal epithelial cells thorough adenoma cells. That is, it promotes growth of normal cells and induces apoptosis of adenoma cells. In addition, on the tumor cells, it has been reported to suppress growth, induce apoptosis and promote histone hyperacetylation. The mechanism of the same has been elucidated.
It has been suggested that the short chain fatty acids directly, or some metabolites thereof generated in the pathway through the acetyl CoA synthesis play a role in the suppression of tumor cell growth (non patent reference 31). In addition, apoptosis inducing activity of the short chain fatty acid has been suggested to be associated with β-oxidization of the same in mitochondria (non-patent references 32-34).
It has been known that the short chain fatty acid is converted to the β-hydroxy fatty acid by means of cell mitochondrial β-oxidization. In has also been known that patients with ulcerative colitis in active phase exhibited impaired fatty acid metabolism and that the content of hydrogen sulfide, which suppress β-oxidization of short chain fatty acid, in the patient's stool was high. In addition, the effect of the short chain fatty acid on rat ulcerative colitis was inhibited by simultaneous administration of a β-oxidation inhibitor. (non patent reference 10).
In view of the apoptosis and cell differentiation inducing effect of the short chain fatty acid, 5-fluorourasil, which is metabolized into butyric acid, and ester derivatives, such as glycerides or sugar ester, of short chain fatty acids have been proposed for treating breast cancer, prostate cancer or leukemia. Those studies were aimed to increase the blood concentration of the short chain fatty acid (non-patent reference 35).
As is mentioned above, the art employed oral administration of various resistant starches or water soluble dietary fibers or enema administration of short chain fatty acid in order to apply the short chain fatty acids to the large intestine.
However, all of thus administrated resistant carbohydrates are not necessarily converted to short chain fatty acids. Some may be converted to carbon dioxide gas, some may be used for bacterial body and some may be converted to the other organic acids such as lactic acid and succinic acid. The short chain fatty acid production efficiency from the resistant carbohydrates are generally low. In addition, the fermentation speed of the resistant carbohydrates is greatly affected by the manner of intake or the existence form of the same in the food. The production ratio between the short chain fatty acids and the other organic acids could vary greatly, for example, if the fermentation speed increases, the amount of the other organic acids can increase. The other organic acids may affect badly. For example, production or accumulation of a large amount of lactic acid may cause diarrhea.
On the other hand, short chain fatty acid may be applied directly to the large intestine by means of intestinal infusion such as enema. However, such procedure allows only intermittent administration. It is difficult to deliver the acid to entire large intestine by the procedure because there are some parts in the large intestine where the acid cannot reach. In addition, it is also difficult to keep the effective concentration of the injected short chain fatty acid in the large intestine for long time.
To date, no practical procedure for delivering the short-medium chain fatty acid to the large intestine in a controlled manner has been developed.
As a polymer of hydroxy fatty acid, poly(β-hydroxybutyric acid) was firstly found by Lemoigne et al and then, the structure of the polymer and the function as energy storage product and as nutrient or energy source in microorganisms were revealed. After the discovery of copolymer of β-hydroxybutyric acid and β-hydroxyvaleric acid from natural bacteria by Wallen et al, many studies on hydroxy fatty acid polymers have been conducted by the art. (non patent reference 36). Accordingly, it was found that microorganisms produce various hydroxy fatty acid polymers. Hydroxy fatty acid polymers are thermoplastic and proposed to be used for manufacturing biologically degradable plastics.
There are some reports concerning hydroxy fatty acid polymers used as energy storage product for a subject other than microorganisms. Patent reference 1 discloses to use emulsion of polyhydroxyalkanoate having particle size of 0.1-10 μm as fat or cream substitutes based on their texture. This reference is silent about the digestion or metabolite energy of the polymer.
Patent reference 2 discloses animal nutrition composition comprising polyhydroxyalkanoate. This reference discloses that polyhydroxyalkanoate or hydroxy fatty acid polymer increases metabolizable energy content of the food and focused on the energy upon intake the same. However, it is silent about the metabolizing mechanism or metabolizing ratio of the polymer in the animal body. Many microorganisms have enzymes capable of depolymerizing poly(hydroxy fatty acids) (non patent reference 37), but there is no report that an animal produces such a depolymerase.
Patent reference 3 discloses orally administrative polyhydroxycarboxylic acid which is used for lowering pH in the intestinal tract by oral administration of the same. This reference discloses various effect of the polymer and all of them are those predicted from the pH lowering effect. According this reference, α-hydroxycarboxylic acids, especially lactic acid are preferable and polylactic acid was used in the working example. It does not mention β-hydroxy short-medium chain carboxylic acid.
Besides they do not mention degradation of poly (β-hydroxy short-medium chain fatty acids) by bacterial flora in the large intestine or the physiological property of the polymer, there are some reports wherein said polymer were administered to animals (non patent references 38-41). Non-patent reference 38 is a report of a study on microorganism proteins for feeding animals and the reference discloses the effect of poly(β-hydroxybutyric acid) produced by the microorganisms as bi-product on the animals. About 65% of poly(β-hydroxybutyric acid) taken by a pig was recovered from the feces and no residual polymer was found in the organs such as liver, kidney or muscle. Accordingly, about 35% of the polymer was speculated as metabolized in the intestine.
Non-patent reference 39 discloses a study employing a copolymer of β-hydroxybutyric acid and β-hydroxyvaleric acid as metabolizable energy. Said copolymer was hardly metabolized in pigs but the water soluble hydrolysates of the polymer obtained with sodium hydroxide could be metabolized. The reference suggests that the metabolism of the copolymer could vary depending on particle size or crystalline form of the copolymer.
Non-patent references 40 and 41 disclose that copolymers of β-hydroxybutyric acid and β-hydroxyvaleric acid could hardly be metabolized in sheep but copolymers having smaller particle size or hydrolysates of the copolymers could be metabolized. However, they are silent about physiological effects of the copolymer on the sheep.
As above discussed, the art has tried to use poly(β-hydroxy short-medium chain fatty acid) as energy source but the prior arts are silent about the other physiological activities of the polymer.
In order to deliver an active ingredient to the large intestine, compositions having mono- or multiple layer coating or capsulated compositions comprising the active ingredient, which are obtainable by coating the ingredient with film or capsule of a polymer that dissolves under specific pH range, such as methacrylic acid copolymer, or a polymer that is digested by bacterial flora in the large intestine, such as chitosan or aromatic azo moiety comprising polymers have been proposed (patent references 4-7). However, those coatings might be degraded in the small intestine or excreted without being degraded in the large intestine. Further, there are some problems in manufacturing the coatings due to the poor solubility of the used polymers in the less-residual volatile organic solvent.
On the other hand, various references disclosed using poly(hydroxybutyric acid) as matrixes for drug delivery system and formulating the same into implants or microspheres including nanospheres and micro capsules (non-patent reference 42).
Orally or enterally administerable immune modulator, which is to be absorbed by macrophage phagocytosis, comprising microsphere matrix made of poly(hydroxybutyric acid) has been proposed (patent reference 8). The reference discloses microsphares having particle distribution range of 1-15 μm so that macrophages can phagocytize the same. However, the reference does not mention to use the polymer for delivering a drug to the large intestine utilizing the property of the polymer being degraded by bacterial flora in the large intestine.    Non-patent reference 1: Aliment. Pharmacol. Ther., 12, 499-507 (1998)    Non-patent reference 2: Biosci. Microflora, 21, 35-42 (2002)    Non-patent reference 3: Curr. Pharm. Des., 9, 347-358 (2003)    Non-patent reference 4: N. Engl. J. Med., 320, 23-28 (1989)    Non-patent reference 5: Altern. Med. Rev., 8, 247-283 (2003)    Non-patent reference 6: Aliment. Pharmacol. Ther., 17, 307-320 (2003)    Non-patent reference 7: Aliment. Pharmacol. Ther., 15, 1253-1262 (2001)    Non-patent reference 8: Int. J. Colorectal Dis., 14, 201-211 (1999)    Non-patent reference 9: JPEN, J. Parenter. Enteral Nutr., 23, S70-S73 (1999)    Non-patent reference 10: J. Gastroenterol. Hepato., 14, 880-888 (1999)    Non-patent reference 11: Eur. J. Nutr., 39, 164-171 (2000)    Non-patent reference 12: Dis. Colon. Rectum, 45, 621-627 (2002)    Non-patent reference 13: J. Gastroenterol., 31, 302-303 (1996)    Non-patent reference 14: Lancet, 356 (9237), 1232-1235 (2000)    Non-patent reference 15: J. Infect. Dis., 179, 390-397 (1999)    Non-patent reference 16: Gastroenterology, 112, A2 (1997)    Non-patent reference 17: Gut, 34, 1215-1218 (1993)    Non-patent reference 18: Gastroenterology, 121, 554-560 (2001)    Non-patent reference 19: N. Eng. J. Med., 342, 308-313 (2000)    Non-patent reference 20: Biosci. Biotechnol. Biochem., 62, 1788-1790 (1998)    Non-patent reference 21: Nutr. Res., 20, 1725-1733 (2000)    Non-patent reference 22: J. Am. Coll. Nutr., 20, 44-49 (2001)    Non-patent reference 23: Dig. Dis. Sci., 47, 1697-1704 (2002)    Non-patent reference 24: Aliment. Pharmacol. Ther., 19, 245-251 (2004)    Non-patent reference 25: Lipids, 30, 163-167 (1995)    Non-patent reference 26: Am. J. Clin. Nutr., 73, 456S-458S (2001)    Non-patent reference 27: J. Nutr., 133, 2180-2183 (2003)    Non-patent reference 28: Gut, 34, 386-391 (1993)    Non-patent reference 29: Gut, 48, 53-61 (2001)    Non-patent reference 30: Gastroenterology, 110, 1727-1734 (1996)    Non-patent reference 31: Eur. J. Biochem., 267, 6435-6442 (2000)    Non-patent reference 32: Cancer Res., 59, 6005-6009 (1999)    Non-patent reference 33: Cancer Res., 54, 3288-3294 (1994)    Non-patent reference 34: J. Biol. Chem., 266, 19120-19126 (1991)    Non-patent reference 35: Life Sci., 63, 1739-1760 (1998)    Non-patent reference 36: Microbiol. Rev., 54, 450-472 (1990)    Non-patent reference 37: Biotechnol. Bioeng., 49, 1-14 (1996)    Non-patent reference 38: Z. Tierphysiol. Tierenahrg.u. Futtermittelkde., 38, 81-93 (1977)    Non-patent reference 39: Ann. Zootech., 48, 163-171 (1999)    Non-patent reference 40: J. Anim. Phys. Anim. Nutr., 81, 31-40 (1999)    Non-patent reference 41: J. Anim. Phys. Anim. Nutr., 81, 41-50 (1999)    Non-patent reference 42: J. Microencapsulation, 9, 73-87 (1992)    Patent reference 1: WO92/09211    Patent reference 2: WO99/34687    Patent reference 3: Japanese Patent Application Laid Open No. H11-092552    Patent reference 4: WO83/00435    Patent reference 5: Japanese Patent Application Laid Open No. H06-179618    Patent reference 6: Japanese Patent Application Laid Open No. H10-324642    Patent reference 7: U.S. Pat. No. 4,663,308    Patent reference 8: Japanese Patent Application Laid Open No. 2000-143538The cited references are incorporated herein by reference.